This is a phase IIa study to assess the safety, tolerability, plasma pharmacokinetics and efficacy of intermittent oral administration of standard levodopa/carbidopa (LD/CD) vs.semi-continuous intra-oral administration of levodopa/carbidopa in patients with advanced Parkinson's disease (PD) who suffer motor fluctuations.The objective of this study is to assess the plasma pharmacokinetics (PK) of continuous intra-oral administration of LD/CD vs. intermittent administration of standard oral LD/CD. For purposes of this study continuous intra-oral administration of LD/CD is defined as oral administration of LD/CD at 5-10 minute intervals.